Then add the essential oil, a drop at a time, until the scent is the strength you want. I usually like to combine a citrus and an herb, like grapefruit and rosemary. You could also use something like tea tree oil, which has some mild antiseptic properties.

Then I leave the finished mixture out on the counter for a couple days. I found that if I put it in a jar right away, it would continue to absorb moisture from the air and would turn into a solid cake I couldn't get out again. By letting it acclimate in a bowl, I can easily break up any clumps before storing.

Put it in a pretty jar and you're done! Use as you would any powdered dishwasher detergent, and never buy the premade stuff again.